方法用Java语言从文件中读取 [英] Method read from file using java language

问题描述

我将提升一个老算法，用java语言，我希望它读取文件中的文本进行加密，所以我会让从文件中逐行读取文本行，然后将它们存储在阵列的方法。我做了这个方法，它的工作原理，但变量2号线正确地读取第一线，但一旦下一行来到它将抹去的第一行，并把第二行我能够这么做讨好??

//将codeS

 专用字节[] 2号线;公众的byte [] readFromFile（）{
    尝试（BR的BufferedReader =新的BufferedReader（新的FileReader（C：\\\\ \\\\用户\\\\只是桌面\\\\ message.txt）））
    {        串sCurrentLine;        而（（sCurrentLine = br.readLine（））！= NULL）{
            2号线= sCurrentLine.getBytes（）;
        }    }赶上（IOException异常五）{
        e.printStackTrace（）;
    }
    返回2号线;
}
 

解决方案

  

我希望它读取文件中的文本进行加密

阅读文本是获得损坏数据的万无一失的方法。读为的字节的。更多关于这下面。

使用Java 7的，它是那样简单：

 最终路径文件= Paths.get（C：\\\\ \\\\用户\\\\只是桌面\\\\ message.txt）;
最后一个字节[] =内容Files.readAllBytes（文件）;
 

---

为什么腐败？

• 首先，一个的的BufferedReader .readLine（）的条新行的;因此，你将加密的内容不会是相同的;


• 第二，你不指定用来读取文件的编码，和的你不C到指定字节编码为en $ C $;和JVM可以选择使用不同的默认编码的和的文件编码。试想一下，如果你使用UTF-8读取窗口1252和德codeD他们的文件会发生什么。

更普遍的：

• 当你读字符串从文件中，所读的并不是字符;这些是字节。和 CharsetDe codeR 之后会去code 这一连串字节 s转换序列字符 S（可能与信息丢失）;


• 当你写一个字符串到一个文件，写的是什么是不是字符;再次，这些都是字节。和 CharsetEn codeR 将连接code这个序列的字符 s转换<序列code>字节秒。

I will enhance an old algorithm which use java language and i want it to read the text from file to encrypt it SO I will make a method that reads the text line by line from file then store them in array. I made this method and it works BUT the variable "line2" reads the first line correctly but once the next line come it will erase the first line and put the second line so what can i do please??

// The CODES

Private byte[] line2;

public byte[] readFromFile (){ 
    try (BufferedReader br = new BufferedReader(new FileReader    ("C:\\Users\\just\\Desktop\\message.txt")))
    {

        String sCurrentLine;

        while ((sCurrentLine = br.readLine()) != null) {
            line2 = sCurrentLine.getBytes();
        }

    } catch (IOException e) {
        e.printStackTrace();
    }     
    return line2; 
}

解决方案

i want it to read the text from file to encrypt it

Reading as text is a surefire way of getting corrupted data. Read as bytes. More on this below.

With Java 7, it is as simple as:

final Path file = Paths.get("C:\\Users\\just\\Desktop\\message.txt");
final byte[] content = Files.readAllBytes(file);

---

Why corruption?

• first of all, a BufferedReader's .readLine() strips newlines; the content you will encrypt will therefore not be the same;
• second, you don't specify an encoding with which to read the file, and you don't specify an encoding to encode to bytes; and the JVM can choose to use a different default encoding and file encoding. Imagine what would happen if you read the file in windows-1252 and decoded them using UTF-8.

More generally:

• when you "read a string" from a file, what is read is not characters; those are bytes. And a CharsetDecoder will then decode this sequence of bytes into a sequence of chars (possibly with information loss);
• when you "write a string" to a file, what is written is not characters; again, those are bytes. And a CharsetEncoder will encode this sequence of chars into a sequence of bytes.

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